“That’s when the [drug] transaction took place,” law-enforcement source said.

The brazen drug deal wasn’t caught on video, but cops were scouring area for other surveillance that might show Hoffman or the suspects afterward, including footage from a townhome directly across street from the star’s nearby pad.

Hoffman’s body was found in his apartment just after 11 a.m. Sunday along with 23 empty bags of heroin and 49 sealed bags of the drug, as well as scores of new and used syringes.